What if coils were at
the bottom?
Bagaimana jika gelung diletakkan di bawah?

Natural
Convection

Air above warmer ground
rises.

Inversion layer.Air near
ground is more dense than
air higher up; no convection
currents to lift pollutants.

Very hot, low-density
air is buoyed upward,
carrying thermal
energy with it.

Conceptual Questions and
Topics

(1) Wind chill factor. (2)
Drapes hung close to a cold window. (3) Clothing.
(4) To keep warm on a cold day, should you wear a fur coat with the
hair inside,
or out? (5) Should you lower the blinds and draw the curtains
on a hot day?

Moderate Temperatures
Near Large Bodies of Water

Warm land is cooled during the day, while
cooler land is warmed at night.

Forced Convection

Hot piston cylinders in automobile
engine are cooled by water forced
around them.

In the example above, the net heat loss is 219 Joules
per second.
How many food Calories of energy will be lost in one hour?
------------------------------------------------------------------------------------------
1 Calorie = 1000 cal
4186 J = 1 Cal

One hour = 3600 seconds Q = 219
x 3600 = 7.88 x 105 J

Number of Calories burned to replace that energy:

7.88 x 105 J / (4186 J/Cal) = 188 Cal

Black
Bodies

Summer clothing:
white reflects
radiant energy better than black.

Until equilibrium is reached, white
stripes on roads are at a lower
temperature than unpainted asphalt.
Wrap an ice-cube in black cloth
and another in aluminum foil and
place both in the sunshine. What
will happen?

Why is the pupil of the
eye black?

Pipes in Solar
Panels are Painted Black

Highly reflecting metal foil keeps
inside temperature low.

Solar
cooker

The Physics of
Fur Coloring

Lemur at left is nocturnal,
so the dark fur poses no
disadvantage in absorbing
excessive sunlight.

Lemur at the right is active
during the day; it points
its belly toward the sun on
cold mornings.

1. The sun goes down, snow falls on cement
playground and on an asphalt road.
Why does the snow on the road melt sooner than on the
cement?

2. Two different materials at the same temperature have different
emissivities.
Which one glows the brightest?

3. Why are fireplace pokers made of iron and not
copper?

4. Some animals have hair which is composed of
solid tubular strands, while
others have hollow, air-filled tubes. Where would
one more likely find
the latter animal: In cold climates, or warm?

5. Steel reinforcement bars add stability to
concrete walls. Do they also
enhance the insulating value of concrete?

6. Two identical cups of cocoa are sitting on a table. One has
a metal spoon
in it and one does not. After five minutes, which
cup is cooler?

7. In Alaska, a lack of snow allowed the ground to freeze down to a
depth
of about one meter, causing buried water pipes to freeze
and burst. Why
did a lack of snow lead to this situation?

8. Several days after the end of a snowstorm, the
roof of a house is completely
covered with snow, another house's roof has no snow.
Which house is
probably better insulated?

9. To keep your hands as warm as possible during
skiing, should you wear
mittens, or gloves? (Mittens, except for the thumb, do
not have individual
finger compartments.)

10. Could one keep warmer in winter wearing a fur
coat inside-out, with the
fur next to the skin?